A protester who swam into the River Thames to disrupt this year's Boat Race could have been killed, according to Olympic rowing champion Matthew Pinsent.
Sir Matthew was assistant umpire during April's race and was immediately behind the university crews on a launch when Trenton Oldfield swam into the paths of the speeding Cambridge and Oxford boats.
Oldfield, 36, from east London, is on trial at Isleworth Crown Court where he denies causing a public nuisance but admits swimming in the path of the crews.
The court heard from a written statement made by Sir Matthew to police just hours after the incident.
He was sharing a launch with umpire John Garrett and behind them were another 25 motorised boats with officials, police, sponsors and camera crews.
Half way through the four-and-a-quarter mile race Sir Matthew, whose job was to look ahead of the crews, saw what he thought was a balloon in the water.
He told Mr Garrett there was debris in the water ahead.
But as they got closer Sir Matthew realised it was a swimmer who had chosen to swim into the path of the boats, he said.
In the statement read by prosecution barrister, Louis Mably, he said: "The risk for the swimmer was great, he could have been killed if he had been struck by an oar or the rigging which is metal.
"The incident caused me alarm as one of my primary roles is the safety of the competitors and public at large.
"I was worried about the safety of the swimmer.
"If he had been hit by an oar or boat he could have cracked his skull, his neck, fallen unconscious and drowned."
Sir Matthew has previously competed in three university boat races and acted as an official in four. He is the winner of four Olympic gold medals.
Umpire Mr Garrett agreed the defendant could have been killed by the boats which were travelling at about 20mph.
"I think he put his life at risk doing what he was doing," said Mr Garrett, who halted the race waving a red flag and using a megaphone.
"He put himself in very high danger and it wasn't just himself he was putting in danger.
"With so much traffic following on that tide there was a risk there may have been crashes between some of the boats."
Mr Garrett said there had been warnings of swimmers the previous year but nothing ahead of 2012's competition which Cambridge eventually won after a restart.